50 PRACTICAL ORGANIC CHEMISTRY Reaction.—A delicate test for ethyl alcohol is the iodoforw reaction. Pour a few drops of alcohol into a test-tube and add about 5 c.c. of a solution of iodine in potassium iodide, and then dilute caustic soda solution until the iodine colour vanishes. Shake up and warm very gently to about 60°. If no turbidity or precipitate appears at once, set the test-tube aside for a time. Yellow crystals of iodoform will ultimately deposit, which have a peculiar odour, and a characteristic star shape when viewed under the microscope. The same reaction is given with FIG. 39. other substances, such as acetone, aldehyde, &c., but not with methyl alcohol. PREPARATION i. Potassium Ethyl Sulphate, CsH6OtSO8.OK Dabit Ann. Ckint. Phys. 1800, (i) 34, 300 ; Claesson, /. prakt. Chem. 1879 (2) 19. 246. 70 grms. (87 c.c.) absolute alcohol.1 50 5, (27 cc.) cone, sulphuric acid. The alcohol is poured into a round flask (J litre) and the •sulphuric acid is slowly added and well mixed by shaking. A 1 For the preparation of methyl potassium sulphate the same quantity of methyl alcohol is used ; in other respects the two processes are identical. The yield is 45—50 grams.